INRIA Sophia Antipolis – Méditerranée Geometrica Monique Teillaud RUG: University of Groningen, NL Institute of Mathematics and Computing Science Gert Vegter Kapteyn Astronomical Institute Rien van de Weijgaert

1.design of algorithms relying on strong theoretical studies guaranteeing the validity of the computed structures 2. production of efficient and robust software to be integrated into 3.experiments on real data

key aspect of the collaboration – computer scientists – mathematicians – astronomers common goals

topological properties of the cosmic web – use triangulations of the 3D flat torus [Caroli, Teillaud] – use alpha-shapes [Da, Yvinec] – compute Betti numbers

topological properties of the cosmic web Alpha, Betti and the Megaparsec Universe: on the Homology and Topology of the Cosmic Web. Rien van de Weygaert, Gert Vegter, Herbert Edelsbrunner, Bernard J.T. Jones, Pratyush Pranav, Changbom Park, Wojciech A. Hellwing, Bob Eldering, Nico Kruithof, E.G.P. (Patrick) Bos, Johan Hidding, Job Feldbrugge, Eline ten Have, Matti van Engelen, Manuel Caroli, and Monique Teillaud. In Transactions on Computational Science XIV, LNCS 6970, pages , Two other publications to appear

hyperbolic periodic triangulations case of the octagon (2D torus of genus 2) – theoretical study of covering spaces – implementation will use triangulations in the hyperbolic plane (to be finalized) [Bogdanov, Devillers, Teillaud] – expected applications to various fields very exciting (and difficult) work, in progress (Bogdanov, Teillaud, Vegter)

strong involvement INRIA: – Manuel Caroli (defended Dec 2010, Gert Vegter in the committee) – Mikhail Bogdanov (started Oct 2010) RUG: – Pratyush Pranav, – Johan Hidding, – Mathijs Wintraecken highly beneficial multidisciplinarity

many visits two public workshops – Subdivide and Tile: Triangulating spaces for understanding the world (46 participants) Nov 2009, Lorentz Center, Leiden, NL – OrbiCG/Triangles Workshop on Computational Geometry, Dec 2010, INRIA Sophia Antipolis - Méditerranée

we are grateful to the Associate Team program of INRIA, which helped us to fruitfully work during three years the collaboration will continue we very much regret that INRIA eventually decided to stop the possibility of having Associate Teams within Europe we are exploring directions and we stay optimistic about finding other funding, albeit on a smaller scale